This invention relates in general to audio circuity and, more particularly to an effective and efficient way of producing an array of unary digital speakers on a semiconductor substrate.
Conventional analog loudspeakers generally rely on the motion of a diaphragm stimulated by some type of motor to reproduce a desired sound. All, or part, of the diaphragm is stimulated in correspondence to an analog electrical signal, typically representing the instantaneous sound pressure that a listener should hear. Analog loudspeakers typically suffer a number of inherent limitations involving, for example, high frequency distortion, non-linearity, and poor power efficiency. Although some solutions have attempted to address these limitations, such solutions have introduced problems of their own, such as non-uniform frequency response, imbalance, phase distortions, power loss and reduction, and increased costs and complexity. Thus, generally, analog loudspeakers have been considered highly inefficient.
The prevalence of high quality digital audio material, and trends in electronic equipment to minimize power consumption for miniaturization and operation from small batteries, have rendered analog loudspeakers somewhat inadequate. Also, conventional analog systems typically require a digital to analog converter (DAC) at some point in the system for the reproduction of digital source material. DACs introduce noise and distortion that adds to that already present in the system, and also add extra cost.
Previously, attempts were made to develop binary digital loudspeakers overcoming the limitations of analog loudspeakers. Such binary digital loudspeakers typically produced marginal improvement over analog systems, but still suffered to some extent from all the limitations previously described, and in some cases introduced further limitations and costs. Many such attempts relied on ratiometric division of a diaphragm or coil turns to correspond to digital bit patterns. These systems suffered from problems with precision and skew resulting in undesired transients and added distortion.
Most conventional digital loudspeaker systems have assumed that binary digital code was the digital signal medium from the input of the device through to the output transducers. Such systems typically suffer from switching transient problems or level change errors, affecting system accuracy and causing large distortion components. Attempts to address such complications with extreme mechanical precision result in high manufacturing costs, and may not achieve the precision required.
Still further attempts were made to produce unary digital loudspeakers, overcoming some of the problems associated with and having higher electrical to sound efficiency than conventional binary digital loudspeakers, and requiring less mechanically accurate speaker structures. Conventional unary speakers generally have a characteristic of being fully xe2x80x9conxe2x80x9d when any voltage or current pulse was applied to the speaker, or fully xe2x80x9coffxe2x80x9d in the absence of any pulse. Typically, conventional unary speaker systems or arrays required a large number of speakers or speaker elements. These approaches were inefficient from both a size and performance perspective. Other conventional systems utilizing piezoelectric transducers and conventional mechanical components commonly utilized separate speakers and drive circuits, reducing system performance and increasing system costs.
Therefore, a high performance unary digital loudspeaker system designed without conventional mechanical structures is now needed; providing cost-effective and efficient performance, and providing the option to integrate multiple speaker elements or other related circuitry, while overcoming the aforementioned limitations of conventional methods.
The present invention provides a unary semiconductor digital loudspeaker comprising a substrate, an electrode disposed upon the substrate, an insulator disposed upon the electrode, and an electrically conductive membrane disposed upon the insulator and forming a chamber between the electrode and membrane.